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心肌细胞晚钠通道的四种开放模式及其对动作电位的影响

李慈珍, 王兴德, 王红卫, 边毓土, 刘远谋

(上海第二医科大学生理教研室，上海200025)

摘要

应用膜片籍技术记录豚鼠游离心室肌细胞钠通道电流，发现晚钠通道电流可分为四种
开放模式:单个短暂开放，散在开放，长时间开放和爆发型开放。它们的开放机率不一样，
其中爆发型的机率为1/2000，其开放时间常数比前三种大。离细胞体的小片膜电压箱制实
验中((inside-out)，亦可观察到晚钠通道的这四种开放模式。它们均可被TTX所阻断。豚鼠心室肌细胞正常动作电位时程呈波动现象，TTX使波动现象基本消失、动作电位时程和有
效不应期缩短、静息电位增加，表明晚钠通道的活动在动作电位平台期的形成中起一定的
作用。

关键词： 游离心室肌细胞; 斑片箱; 晚钠通道电流; 模式

FOUR TYPES OF LATE Na CHANNEL CURRENT IN ISOLATED VENTRICULAR MYOCYTES WITH REFERENCE TO THEIR CONTRIBUTION TO THE LASTINGNESS OF ACTION POTENTIAL PLATEAU

LI CI-ZHEN, WANG XING-DE, WANG HONG-WEI, BIAN Yu-Tu, LIU YUAN-Mou

(Department of Physiology, Shanghai Second Medical University, Shanghai 200025)

Abstract

Patch clamp technique was employed to record single Na channel current in isolated guinea-pig ventricular myocytes. Four types of late Na channel currents were observed with whole cell and inside-out recording, which are (1) isolated brief openings, (2) scattered openings, (3) long openings and (4)
bursts. The occurrence frequencies of the four types were different. Bursts appeared about 1 in every 2 000 depolarizations, with an open time constant longer than others. However, all the four types of late current openings, as well as the early openings occurring immediately upon depolarization, could be
blocked by tetrodotoxin. It was also found that at a certain stimulation frequency, normal action potential duration (APD) was not invariable as supposed before, but varied from stimulation to stimulation. Special Na channel blocker, TTX, shortened the APD and refractory period and abolished the dispersion. The above results suggest that the activities of the various types of late Na channel play an important role in the formation of action potential plateau.

Key words: isolated ventricular myocytes; patch clamp; late Na channel current; model

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引用本文：

李慈珍, 王兴德, 王红卫, 边毓土, 刘远谋. 心肌细胞晚钠通道的四种开放模式及其对动作电位的影响[J]. 生理学报 1997; 49 (2): .

LI CI-ZHEN, WANG XING-DE, WANG HONG-WEI, BIAN Yu-Tu, LIU YUAN-Mou . FOUR TYPES OF LATE Na CHANNEL CURRENT IN ISOLATED VENTRICULAR MYOCYTES WITH REFERENCE TO THEIR CONTRIBUTION TO THE LASTINGNESS OF ACTION POTENTIAL PLATEAU . Acta Physiol Sin 1997; 49 (2): (in Chinese with English abstract).